1. Field of the Invention
The present invention is directed to monitoring the contaminant concentration in gases. More particularly, the present invention is directed to monitoring concentrations of selected contaminants in compressed air for respiratory use.
2. Description of the Prior Art
Many systems have been devised and are in use for determining contaminant concentrations in gases. Such systems often include pumps to meter a specified amount of gas through a testing material which changes color upon contact with a particular contaminant. These systems generally require a vial, which is inserted into the testing unit. A read-out is obtained from the vial which may be directly or indirectly used to determine the contaminant presence or concentration. Examples of such systems and the vials used as detector tubes are disclosed in a certain products bulletin of National Draeger, Inc., entitled "Gas and Vapor Detection Products".
Other systems in use in industry include in-line process sensors which determine a change in a characteristic of a gas being tested which is indicative of a change in contaminant concentration. These types of systems are useful where the contaminant itself is colored and, thus, changes in light reflection or transparency can be used to determine concentrations.
In other systems, electrical properties such as resistance or conductivity are measured against a standard to determine a concentration of the contaminant. Such prior art systems generally function quite well in the areas of suggested use. However, there is a need in the art for a system which is easily adaptable for use in measuring contaminant concentrations in compressed air and which can be used reliably by persons without particular skill or training in the use of air monitoring systems. It is apparent that with regard to compressed air which is used for breathing, for instance, the water vapor, oil, carbon monoxide, and carbon dioxide content of the compressed air should be monitored since the presence of such contaminants in even small amounts can be detrimental to the user. Thus, the present invention is directed to a system which can be easily utilized and will accurately test compressed air for the presence of various contaminants.